This disclosure relates to throttle devices for adjusting the amount of air flow through an engine's air intake system, and methods for manufacturing the same.
An example of a conventional throttle device (for example, Japanese Laid-Open Patent Publication No. 2002-371866) will now be described. As shown in FIG. 21, a throttle device 110 includes a throttle body 111, a motor 112 and a reduction gear mechanism, wherein the reduction gear mechanism includes a motor pinion 112p, a counter gear 113 and a throttle gear 114. The throttle gear 114 is integrally attached to a throttle shaft 120. The motor 112 rotates the throttle shaft 120 via the reduction gear mechanism so that a throttle valve attached on the throttle shaft 120 is rotated. As a result of the throttle valve rotation, the amount of intake air flowing through an intake passage in the throttle body can be adjusted.
A spring member 115 is interposed between the throttle gear 114 and the throttle body 111. The spring member 115 is configured to bias the throttle gear 114 to an initial opening angle.
The throttle body 111 is provided with a screw 116 and a screw 117. The screw 116 is a fully closed opening angle restricting screw for restricting a fully closed angle of the throttle valve (throttle gear 114). The screw 117 is an initial opening angle restricting screw for restricting the initial opening angle of the throttle valve. The throttle gear 114 includes a gear stopper 114a that is able to abut the fully closed opening angle restricting screw 116 such that the throttle gear 114 is restricted from rotating past a fully closed angle. The spring member 115 includes a stopper 115a that is able to abut the initial opening angle restricting screw 117 such that the throttle gear 114 is restricted from rotating past an initial opening angle. The fully closed opening angle restricting screw 116 may be moved forward or backward for the fully closed angle to be adjusted, respectively. Similarly, the initial opening angle restricting screw 117 may be moved forward or backward for the initial opening angle to be adjusted, respectively.
According to the conventional throttle device, the fully closed opening angle restricting screw 116 and the initial opening angle restricting screw 117 components are necessary to ensure the accuracy of the fully closed angle and the initial opening angle. For this purpose, a large number of components are employed for conventional throttle devices, which consequently result in complexity, high cost of manufacturing, and additional need for maintenance.